We have used reductive coupling with cyanoborohydride to glycosylate asparaginase. We reported recently (Marsh et al., JBC 252, 7678, 1977) that lactosylated asparaginase showed higher thermal stability and resistance to asparaginase modified by coupling N-acetylneuraminyl lactose is cleared more slowly. The more rapid clearance of lactosylated enzyme is in accord with Ashwell's demonstration of a galactosyl receptor in liver parenchymal cells. The reason for the slower clearance of NAN-lactosylated enzyme is less obvious. The effect might be due to a decrease in pI caused by introducing sialyl residues, but work by others on the effect of pI on protein clearance has been inconclusive. We have prepared succinylated and acetylated asparaginase and determined clearance times in mice and isoelectric points. Acetylation and succinylation both accelerate clearance, although the effect is much greater in the case of succinylated enzyme. The central conclusion of this work is that succinylated asparaginase, with a lower pI like that of NAN-lactosylated enzyme, is cleared much more rapidly than native enzyme. Since this is the reverse of what was seen with NAN-lactosylated enzyme, the slower removal seen with that material cannot be based on some simple relationship between clearance an pI.